1. Field of the Technology
The present technology relates to an image display apparatus in which a display screen for displaying images is formed. In addition, the present technology relates to an image display apparatus in which a planar optical member is arranged between a liquid crystal panel and an illumination light source illuminating the liquid crystal panel, and more particularly, to an image display apparatus capable of efficiently suppressing thermal deformation of the optical member.
2. Description of the Related Art
Japanese Unexamined Patent Publication JP-A 10-326517 (1998) discloses an image display apparatus having a back-side illumination unit which includes a sheet-shaped optical member, a lamp housing, and a plurality of spacer pins. The plurality of spacer pins are arranged on the bottom inner portion of the lamp housing so as to prevent the central portion of the optical member from being bent towards the bottom inner portion of the lamp housing. The optical member extends in a planar direction thereof due to thermal expansion resulting from a temperature rise. The linear expansion coefficient of the optical member is larger than those of the other members.
When a bezel, which covers the optical member, is configured such as to be a part of the lamp housing, or to connect to the lamp housing, and is provided to be sufficiently larger than the optical member outwardly in the planar direction thereof, the amount of extension of the optical member resulting from the thermal expansion of the optical member can be accommodated in an inner space of the bezel.
In recent years, there has been an increasing demand for image display apparatuses having a larger display screen and a small thickness. In such image display apparatuses, it is desirable to further decrease the size of the bezel provided outwardly in the planar direction of the display screen, and a narrower bezel is demanded.
Japanese Unexamined Patent Publication JP-A 2004-233828 discloses a liquid crystal display apparatus which includes a lamp housing, a light diffuser plate, a front sheet, a liquid crystal panel, and a plurality of lines of pillars. The plurality of lines of pillars are formed at positions where they support a central portion of the light diffuser plate provided above the pillars and the surrounding portion of the central portion. Among the plurality of lines of pillars, the length of the pillars supporting the central portion is larger than the length of the pillars supporting the surrounding portion.
The technique of realizing a narrower bezel as disclosed in JP-A 10-326517 has a problem in that extension of the optical member resulting from thermal expansion or the like cannot be allowed.
The technique disclosed in JP-A 2004-233828 has a problem in that although bending can be allowed and the bending direction can be regulated, the central portion of the light diffuser plate comes into contact with the liquid crystal panel.
In addition, techniques concerning temperature control performed in an image display apparatus are disclosed in Japanese Unexamined Patent Publications JP-A 2000-171773, JP-A 2001-227494 and JP-A 2005-17555.
JP-A 2000-171773 discloses a liquid crystal display apparatus which includes a liquid crystal panel, an illumination unit including a fluorescent tube which is an illumination light source, a temperature sensor that detects an ambient temperature of the fluorescent tube, an optical sensor that detects a luminance on the surface of the liquid crystal panel, a cooling unit for cooling down the illumination unit, and a control circuit for controlling the cooling unit in accordance with the detection results from the optical sensor and the temperature sensor. The liquid crystal display apparatus is capable of maintaining the maximum luminance by controlling the ambient temperature of the fluorescent tube.
JP-A 2001-227494 discloses a display apparatus which uses a PDP (Plasma Display Panel) and which includes a cooling fan for cooling down a casing of the display apparatus, an outside-air temperature detection section that detects the outside-air temperature of the display apparatus, a determining section that determines the rotation speed of the cooling fan corresponding to the detected outside-air temperature, and a fan control unit that gradually increases the rotation speed of the cooling fan from a non-rotating state to the rotation speed determined by the determining section within a predetermined period. The display apparatus diminishes discomfort resulting from the rotation sound of the fan.
JP-A 2005-17555 discloses a display apparatus which includes an approximately box-shaped main body, a liquid crystal panel and a backlight disposed on a front side of the main body, a control unit disposed on a rear side of the main body, and a first temperature sensor for detecting the temperature of the control unit. When the first temperature sensor detects a temperature equal to or higher than a first setting value, the control unit decreases the power inputted to the backlight. Thus, it is possible to decrease the temperature of the control unit to a temperature lower than the first setting value.
In recent years, liquid crystal display apparatuses have been increased in size and luminance as well as narrowed in bezel size. In such liquid crystal display apparatuses, there is a problem in that a planar optical member arranged between a liquid crystal panel and an illumination light source illuminating the liquid crystal panel is thermally deformed to an unallowable extent accompanied by heat generation of the illumination light source, whereby the quality of images displayed on the liquid crystal panel deteriorates.
However, none of the display apparatuses disclosed in JP-A 2000-171773, JP-A 2001-227494, and JP-A 2005-17555 are configured to perform temperature control focusing on the thermal deformation of the optical member. Therefore, there is a problem in that deterioration of the image quality due to the thermal deformation of the optical member is not suppressed efficiently, and thus, noise produced by the cooling unit is not decreased.
Moreover, the display apparatuses disclosed in JP-A 2000-171773, JP-A 2001-227494, and JP-A 2005-17555 are configured to control only one of the cooling unit and the illumination light source. Therefore, there is a problem in that the control is not performed with high efficiency or high accuracy.